Nobel Metal Nanoparticles/Nitrogen-Doped Porous Graphene Composites:Preparation And Their Application In Electrochemical Sensors

Nanocarbon materials for instance graphene,carbon nanotubes/fibers,and nanoporous carbons have been extensively studied as electrode materials for electrochemical devices such as sensors or biosensors,due to their low cost,abundant structural variety,chemical and thermal stability,and conductivity.Among nanocarbon materials,graphene（GR）is a 2D nanosheet of sp2-hybridized carbon atom.It is widely used as the basic building block of 1D and 3D materials and longrange π-conjugation in graphene endows it with extraordinary properties such as high surface area,very fast charged carrier mobility and high thermal conductivity.In order to facilitate GR suitability for different applications,modification into porous structure and heteroatom doping are some of the ways being adopted.Porous GR（PGR）is a GR sheet with some pores/holes within the atomic plane.It is a modified GR sheet where the absence of carbon atoms within the plane creates some holes/pores.The presence of pores in GR serves to increase the specific surface area,and alleviation of the Van Der Waals interactions between the inter-sheets,thus reduces the stacking of graphene nanosheet layers and provides more surface active sites for catalysts and also favors ion transport.On the other hand,the heteroatom doping was adopted.The heteroatom doping could change the electronic properties of carbons and produce additional functional groups on the carbon surface,and this greatly enhances the electrochemical performance of PGR.Furthermore,in order to improve properties and increase the activity of Ndoped PGR,the nanoparticles（NPs）like noble metals were deposited into N-doped PGR sheets.This strategy has been attracted a lot of attention and achieved valuable results.Based on the previous studies,we have studied the electrochemical properties of Pt/NPGR and PtPd/HNPG and used them as sensors to determine Tadalafil（TAD）and Glucose respectively.In the second chapter,the Pt/NPGR-X electrodes were prepared through several steps as follows,initially,N-doped porous graphene（NPGR）was prepared by using SiO₂ as a template to support of different sizes as template materials for the GO to synthesize GO/SiO₂ particles,followed by pyrolysis with ammonia（NH₃）after theremoval of the SiO₂ template.Finally,Pt NPs supported in NPGR to synthesize Pt/NPGR-X electrodes.The structural characterization showed porous structures in all the catalysts but with different surface areas in which Pt/NPGR-120 had a large surface area due to its smaller particles.In addition,electrocatalytic performances were determined for sensitive TAD and the Pt/NPGR-120 electrode illustrated high performance in comparison to the other electrodes.This method provides a good way for the selective,sensitive,and a simple approach to detect TAD with low detection at a wide linear range.Lastly,in the third chapter,we used an easy,low cost and effective method for synthesizing the porous holey nitrogen-doped graphene（PHNG）with threedimensional（3D）structure via a direct pyrolysis of a mixture of urea and magnesium acetate tetrahydrate.The PtPd nanoparticles supported into PHNG composites with the different atomic ratio of Pt: Pd to synthesize PtPd/PHNG-X electrodes,and then directly used as a non-enzymatically sensor of glucose.The PtPd/PHNG-2 electrode shows high direct oxidation activity towards the glucose,achieving high sensitivity,long linear range,response time,low limit of detection,as well as high selectivity.